Author Options:

Limit current for a circuit using 5V 450mA power supply? Answered

Have a 5V DC power supply that is rated for 450mA +-50mA...want to use it for a 5V circuit with an Attiny85 and a couple of LEDs. I don't think I could use a voltage regulator since that will bring the voltage to lower than 5V, but the current seems high for use in a small circuit. How can I limit it? Using a resistor? Or should I not bother?


4 Replies

The Skinnerz (author)2012-12-07

Your circuit will only draw the current that it needs, 450mA is just the maximum rating of the power supply, so no additional current limiting should be needed. If your circuit only draws 50mA, then the the supply will only provide 50mA.

Select as Best AnswerUndo Best Answer

mrmerino (author)2012-12-07

If you get worried just put a fuse rated to just below the threshold current of the device you're using in series with it. That way the fuse will go before the device.

Select as Best AnswerUndo Best Answer

rickharris (author)2012-12-07

Your circuit will DRAW whatever current it needs - Excess is just not used.

HOWEVER for micro processors in general it is recommended to use a regulated voltage - If your just lighting a couple of small LEDs your probably OK. If your operating bigger things like motors your voltage will vary with the load.

Your right that to have a regulated 5 volts you need to over supply the regulator so it can operate.

Select as Best AnswerUndo Best Answer